Prime mover system utilizing bis (trifluoromethyl) benzene as working fluid

ABSTRACT

An anti-pollution heat engine including a prime mover system wherein the working fluid comprises bis (trifluoromethyl) benzene.

United States Patent Conner et al. 1 Jan. 2, 1973 s41 PRIME MOVER SYSTEM UTILIZING [56] References Cited TRIFLUOROMETHYL BENZENE K FLUID UNITED STATES PATENTS [75] Inventors: Rex C. Conner, Englewood; Louis geggggg 2 32: 3": at "60/36 L. Ferstand Rid e ood both of I ac eta e ..60/36 X g 3,234,734 2/1966 Buss eta]. ..60/36 N-J- 3,516,248 6/1970 McEwen ..60/36 A H l ho P d t C ti [73] Sslgnee z fsg r g S Primary Examiner-Edgar W. Geoghegan v Assistant Examiner-A. M. Ostrager [22] Filed: Jam 4, 19 Attorney-Ralph D. Dinklage et a].

[2]] App]. No.1 215,438 [57] ABSTRACT An anti-pollution heat engine including a prime mover system wherein the working fluid comprises bis [58] mido; a ;"'""'"'iiiiiii'iiiii'ifii' 60/36 miflwmthy" 11 Claims, No Drawings PRIME MOVER SYSTEM UTILIZING BIS (TRIFLUOROMETIIYL) BENZENE AS WORKING FLUID The present invention relates to prime mover systems for the conversion of heat into work by the expansion and condensation of, a heated pressurized vapor.

Conventional internal combustion engines operate by explosive consumption of a fuel in a cylinder so as to move a piston which in turn rotates a shaft, often to drive a vehicle. Because of the varied conditions ofexplosion due to changes in load, e.g. during acceleration, idling or normal driving, combustion frequently varies from the ideal, the consumption of the fuel being incomplete so that incompletely oxidized substancesare discharged into the atmosphere with attendant pollution.

A vapor cycle heat engine operating to drive an expander, e.g. a turbine, piston engine, or the like, wherein heated pressurized water vapor is used as the working fluid in a prime mover system, commonly called an external combustion engine, is quite efflcient in its combustion of fuel, i.e. the fuel is substantially fully consumed; in addition, it is relatively flexible in the nature of the fuels which may be used. However, using water as the working fluid necessitates very high temperatures and pressures to achieve reasonable efficiencies for the conversion of heat energy to work and this in turn requires special safety measures and special equipment, including expensive alloy metals. In addition, at steam temperatures above 650F. conventional lubricants and gasketing material break down.

In an effort to overcome the problems with steam, other working fluids have been proposed but they introduce other problems of their own, e.g. breakdown of the fluid upon prolonged heating, chemical reaction with metal materials of construction and with conventional gasketing materials, limited efficiency, toxicity, flammability, or the like.

Where the working fluids have not been miscible with the lubricants used in engines, it has been necessary to maintaina high degree of oil-water separation to.

prevent the coating of condenser tubes. Coatings accumulating in condenser or regenerator tubes adversely affect heat transfer, necessitating the construction of units larger than necessary for the transfer of heat from the working fluid to the cooling medium.

It is accordingly an object of the present invention to provide novelworking fluids in prime mover systems utilizing external combustion to put thermal energy into the fluid for conversion to motive power.

A further object of the invention is to provide a safe working fluid for a vapor cycleengine such as the Rankine Cycle engine for a vehicle, boat or other power equipment, powered by an efficient, inexpensive, safe, low emission, prime mover system which can be powered by the' consumption of a variety of readily available fuels such as fuel oil, diesel fuel, kerosene, gasoline, natural gas, propane, butane, alcohol, oil and the like, or solid fuels, to minimize pollutionof the atmosphere. A further object of this invention is to provide a working fluid which is miscible with conventional high temperature lubricants and which will not react chemically with themat anypressure or temperature.

In accordance with the present invention, there is provided a conventional prime mover system such as a Rankine Cycle engine to provide mechanical work, except that the working fluid comprises a compound of the formula F55 XII wherein X is CH, or CF,,, and n is 0 or I.

Preferably no two substituents on the benzene ring are in adjacent positions, whether n is 0 or i. Preferably n is 0, in which case the preferred compound is bis(trifluoromethyl)benzene wherein the trifluoromethyl groups are in either meta or para-positions.

The working fluid can comprise individual pure isomers such as l,3-bis(trifluoromethyl)benzene or it can comprise mixtures of isomers as well as blends with other substances such as hydrocarbons or fluorinated hydrocarbons in an effort to reduce the amount of trifluoromethylbenzene required, or the like.

It is most surprising that the trifluoromethylbenzenes are suited for use over prolonged periods of time at high temperatures, e.g. about 500 to 700F. This can be seen from the following: while benzene per se has acceptable physical properties for use as a working fluid, it is highly flammable so as to make it unacceptable on that score. Its stability upon prolonged exposure to high temperatures, however, is quite satisfactory. By introducing a trifluoromethyl group on the ring, the resulting trifluoromethyl-benzene is indeed of reduced flammability but it is markedly decomposed in a relatively short time upon being held at 750F. Surprisingly, by doubling the trifluoromethyl function the stability, instead of getting still poorer, improves dramatically.

The novel working fluids are especially useful in turbines and, compared to other working fluids, generally give a higher horsepower at a particular rpm or, for a given horsepower output, permit the turbine to operate at a lower rpm. The prime mover system may be used for automobile vehicles, boats or for purposes other than motive power such as in electric generators, powered equipment, and the like, wherever other such systems or internal combustion engines have heretofore been used. The motive power, when involved, may drive any shaft including especially the drive shaft of vehicles such as automobiles.

The bis-(trifluoromethyl)benzenes are low melting and high boiling which is desirable in engines which may have to stand, without operating, in a variety of climates. They are non-corrosive upon the ordinary metals involved in engines and cooling systems such as automobile radiators, e.g. carbon steel, copper and aluminum, even upon prolonged exposure at high temperature, as can readily be seen from the following table: TABLE Tempernturo, Time, Remarks re Material Metal F. hours starting material (I 1': Carbon stop-L 600 1, 052 No decomposition.

Some its nl ovo (lo 750 281.3 0.6%

decomposition. l)o 350 864 No (Ir-composition. l)0 350 864 D0. l)o stool 700 (iti Do. Do. A- 5l-5 stool 700 till Do.

The novel working fluid is miscible with conventional high temperature lubricants but inert relative thereto. As a result, it acts continually to dissolve any coatings of the lubricant which may tend to build up in the boiler, the throttle valve, the expander or in the cooling units. In a high speed turbine, where clearances are critical, this is particularly advantageous. In such a system only excessive accumulations of lubricant in the working fluid need be separated. This can be accomplished by demisters, cyclonic type separators and the like which provide only partial separation, located at any point in the system where the temperature of the vaporized fluid is below the dew point of the lubricant and above the dew point of the working fluid.

The following example illustrates practice of the invention:

EXAMPLE l,3-Bis(trifluoromethyl)benzene of 99 percent purity can be used as the working fluid in a turbine, entering a boiler at 235F and leaving as a vapor at 500F and 270 psia. The vapors are superheated to 650F at that pressure and then are expanded through the blades of a turbinewhose shaft is caused to rotate and perform work. The expanded vapor which is still hot passes through a regenerator where it undergoes heat exchange with liquid working fluid, the vapor thereby being cooled; upon further cooling the vapor condenses, falling back to 237F and 14.7 psia at which point it enters a reservoir. From the reservoir the liquid is pumped to the boiler, on the way being subjected to heat exchange with the expanded still warm vapor referred to previously.

Substantially similar results are achieved if the expansion of the gas takes place against a reciprocating piston which is slidably mounted between two positions, the expansion causing the piston to move to its second position and rotate a crank-shaft in doing so, the shaft driving a prime mover. Similarly the expansion can be utilized to rotate a helical screw.

In place of meta-bis(trifluoromethyl)benzene, the para-isomer, or mixtures thereof, give substantially similar results and such mixtures are generally less expensive. Blends with benzene, toluene, or the like are also satisfactory working fluids, although preferably the novel compounds comprise a major proportion of the working fluid. Other compounds which may be used in accordance with the invention include 1,3,5- tris(trifluoromethyl )benzene; l,3-bis(trifluoromethyl S-methylbenzene, and the like.

It will be appreciated that the instant specification and examples are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention.

What is claimed is: 1. In a prime mover system wherein heat is converted to mechanical work, the syst em i cludinga closed circuit containing a reservoir 0 wor ing fluid, means for wherein X is CH or CF and n is 0 or 1.

2. A system according to claim 1, wherein the fluid comprises a mixture of compounds falling within the general formula.

3. A system according to claim 1, wherein the fluid comprises a blend wherein a major proportion thereof is one or more compounds falling within the general formula.

4. A system according to claim 1, wherein the expander is a turbine, piston engine or helical screw.

5. A system according to claim 1, wherein the expander is a turbine.

6. A vehicle driven by a prime mover system according to claim 1.

7. In the conversion of heat into motive power by vaporizing a portion of the fluid from a reservoir and then allowing said fluid vapor to expand, condense and return to said reservoir, said expansion moving a member, the improvement which comprises heating said fluid to a temperature of about 500 to 700F, said fluid comprising a compound of the formula XII wherein X is CH or CP and n is 0 or 1.

8. A process according to claim 7, wherein the fluid comprises a mixture of compounds falling within the general formula.

9. A process according to claim 7, wherein the fluid comprises a blend wherein a major proportion thereof is one or more compounds falling within the general formula.

10. A process according to claim 7, wherein the expander is a turbine, piston engine or helical screw.

11. A process according to claim 7, wherein the expander is a turbine.

4 I l l t 

2. A system according to claim 1, wherein the fluid comprises a mixture of compounds falling within the general formula.
 3. A system according to claim 1, wherein the fluid comprises a blend wherein a major proportion thereof is one or more compounds falling within the general formula.
 4. A system according to claim 1, wherein the expander is a turbine, piston engine or helical screw.
 5. A system according to claim 1, wherein the expander is a turbine.
 6. A vehicle driven by a prime mover system according to claim
 7. In the conversion of heat into motive power by vaporizing a portion of the fluid from a reservoir and then allowing said fluid vapor to expand, condense and return to said reservoir, said expansion moving a member, the improvement which comprises heating said fluid to a temperature of about 500 to 700*F, said fluid comprising a compound of the formula wherein X is CH3 or CF3, and n is 0 or
 1. 8. A process according to claim 7, wherein the fluid comprises a mixture of compounds falling within the general formula.
 9. A process according to claim 7, wherein the fluid comprises a blend wherein a major proportion thereof is one or more compounds falling within the general formula.
 10. A process according to claim 7, wherein the expander is a turbine, piston engine or helical screw.
 11. A process according to claim 7, wherein the expander is a turbine. 